The present invention is directed generally to fasteners for joining two or more structures together and, more particularly, to lock-pins, such as lock-pins that are installable and removable from a single side of a joint or other installation.
There are many ways that lock-pins and similar devices can be used to join two or more structures together at a common joint. Lock-pins for this purpose generally have a head of some type toward a head end, a locking element of some type toward an opposite tip end, and a cylindrical shaft therebetween. Such lock-pins are typically installed by inserting the tip end through a hole on the xe2x80x9cnear-sidexe2x80x9d of a joint until it emerges on the xe2x80x9cfar-sidexe2x80x9d of the joint. The locking element is then installed or otherwise implemented toward the tip end to retain the lock-pin in the joint, thereby making a structural connection.
FIGS. 1A through 1D collectively are side views of some common lock-pins in accordance with the prior art. FIG. 1A, for example, illustrates a lock-pin 100 having a head 101 and a cylindrical shaft 102. A bore 103 extends perpendicularly through the tip end of the shaft 102 and can removably receive a coffer pin 104 or a similar device as a separate locking element. Lock-pin devices similar to the lock-pin 100 can be used for myriad applications, including shackle-type installations. U.S. Pat. Nos. 5,114,260 to Hart et al., 5,460,418 to Falls, 4,102,124 to Swager, and 6,023,927 to Epstein disclose but a few such lock-pin devices.
Other lock-pins are similar to the lock-pin 100, except they do not use a cotter pin type locking element. U.S. Pat. No. 1,799,934 to Strid, for example, discloses a lock-pin that uses a continuous wire spring resiliently inserted through the bore 103 as a locking element that retains the pin once installed. U.S. Pat. No. 2,399,119 to Howell, U.S. Pat. No. 4,205,586 to MacNeill, and U.S. Pat. No. 5,599,150 to Edwards et al., all embody designs similar to Strid. One advantage of these lock-pins over the lock-pin 100 is that their locking elements can be installed, removed, and reinstalled through the bore 103 more easily than the cotter pin 104.
In many applications, it will be desirable to install a lock-pin through a hole where no access exists to the far-side of the hole where the tip of the lock-pin emerges. For ease of reference, such an installation will be referred to throughout this disclosure as a xe2x80x9cblindxe2x80x9d installation. A common feature of all the prior art lock-pins discussed above is that they require access to the tip end of the shaft 102 after the shaft has been inserted through a hole so that a separate locking element can be installed in the bore 103. This feature renders these lock pins essentially useless in blind applications. Another common shortcoming associated with all these lock-pins is that the separate locking element, whether it be a cotter pin or a wire spring, can easily be lost or misplaced, thereby frustrating installation and again rendering the lock-pin essentially useless.
FIG. 1B is a side view of a lock-pin 110 in accordance with the prior art that does not use a separate locking element. The lock-pin 110 has pull-ring 111 moveably attached toward the head end of a cylindrical shaft 112. A rotatable locking element 114 is rotatably attached toward the tip end of the shaft 112, and a coil spring 115 is coaxially disposed over the shaft in compression against the locking element. The locking element 114 is rotated to an unlocked position in axial alignment with the shaft 112 for installation of the lock-pin 110 through a hole (not shown). After installation, the locking element 114 is rotated approximately 90 degrees to a locked position as illustrated to prevent the lock-pin 110 from backing out of the hole. The coil spring 115 keeps the locking element 114 in this locked position unless or until the locking element is manually rotated to the unlocked position.
U.S. Pat. No. 5,437,515 to Kuramoto et al. discloses a lock-pin that is similar to the lock-pin 110 shown in FIG. 1B. In Kuramoto, however, the locking element is maintained in the locked position by way of a positioning member inserted radially through the locking element. U.S. Pat. No. 5,112,155 to Jackson and U.S. Pat. No. 4,822,197 to DeMartino et al. have locking mechanisms similar to that disclosed in Kuramoto, but they do not require a positioning member. Although lock-pins like that shown in FIG. 1B do not require a separate locking element as does the lock-pin shown in FIG. 1A, they nevertheless still cannot be used as a removable fastener in blind installations where there is no access to the tip end of the shaft 112 to rotate the locking element 114 as necessary to retain or remove the lock-pin.
FIGS. 1C and 1D illustrate some prior art lock-pins that can be installed from only one side of an installation application and thus are useable in blind applications. Shown in FIG. 1C, for example, is a quick-release pin 120 that can be installed with access to only the near-side of a joint. The quick-release pin 120 is similar, but not identical, to the lock-pin disclosed in U.S. Pat. No. 5,845,898 to Halder et al. The quick-release pin 120 consists of a spring-loaded plunger 125 that movably extends longitudinally through the center of a cylindrical shaft 122 from a head end toward a tip end. By pressing the spring-loaded plunger 125, two balls 124 located at the tip end of the shaft 122 are allowed to retract radially inward until flush with the outer surface of the shaft, thereby allowing the quick-release pin 120 to be inserted through a hole (not shown). When the spring-loaded plunger 125 is released, it pushes radially outward against the two balls 124 causing the balls to protrude radially outward and act as locking elements that retain the lock-pin 120 in the hole.
One shortcoming of the quick-release pin 120 of FIG. 1C is that manufacturing considerations prevent the balls 124 from protruding very far outboard of the shaft 122. As a result, the quick-release pin 120 cannot hold two structures together effectively unless the shaft 122 is a very close fit in the corresponding hole through which the quick-release pin is inserted. Hole tolerances often cannot be held close enough to make this type of lock-pin useful or cost effective. In addition, the ball-type locking elements of this type of lock-pin are prone to release prematurely where vibration or substantial axial loads are present. Furthermore, the complicated assembly of the quick-release pin 120, in addition to its plurality of elements, can make it expensive to manufacture and hence costly to the consumer.
FIG. 1D is a side view of yet another lock-pin 130 in accordance with the prior art that can be used in blind applications. The lock-pin 130 has a pull-ring 131 moveably attached toward a head end of a cylindrical shaft 132, and a single spring-loaded ball 134 located toward a tip end of the shaft. The lock-pin 130 is intended to be installed by simply pressing it into a hole with sufficient force to overcome the spring-loaded ball 134 causing it to retract into its hole. The lock-pin 130 is accordingly removed by pulling on the pull-ring 131 with a force of similar magnitude. As should be apparent to those of ordinary skill in the art, the lock-pin 130 is a poor choice for those applications that could be subjected to a substantial axial load in service, because of the tendency for such an axial load to overcome the spring-loaded ball 134 and disengage the lock pin.
In addition to the various prior art lock-pins discussed above, a safety hitch-type lock-pin having a shaft with a coaxial longitudinal bore is disclosed in U.S. Pat. No. 5,199,733 to DeLorme. In DeLorme, a lock-rod is inserted through the bore from the head end and is connected to two flanges embedded into respective slots toward the tip end. Rotation of the lock-rod causes the flanges to rotate outward, thus retaining the lock-pin after installation. This sophisticated mechanism consists of several moving parts, is relatively difficult to manufacture, and hence is relatively costly. In light of the shortcomings associated with prior art lock-pins as discussed above, a simple yet robust lock-pin, suitable for use in blind applications, would be desirable.
The present invention overcomes limitations of the prior art by providing a lock-pin that, in selected embodiments, can be used in blind applications and still carry substantial axial loads. In one embodiment, the lock-pin comprises a pin having a first end spaced apart from a second end and a cylindrical shaft portion at least partially disposed between the first and second ends. The shaft portion defines a cross-section dimension and a longitudinal axis of symmetry. A bore extends through the shaft portion in a generally longitudinal direction non-collinear with the longitudinal axis of symmetry.
In one aspect of this embodiment, the lock-pin further comprises a rotatable key at least partially rotatably disposed within the bore. The rotatable key includes an actuating portion positionable toward the first end of the pin and a retainer portion positionable toward the second end of the pin. The rotatable key is optionally rotatably positionable to rotate the retainer portion to a first position entirely within the cross-section dimension of the shaft portion or to a second position at least partially outside of the cross-section dimension of the shaft portion.
In one embodiment of the invention, the lock-pin can join a first structure having a first hole to a second structure having a second hole. The first and second holes should have diameters at least slightly greater than the cross-section of the shaft portion of the pin, and the first hole should be axially aligned with the second hole. In one aspect of this embodiment, the rotatable key of the lock-pin is initially rotated so that the retainer portion is in the first position. The shaft portion of the pin is then inserted through the first and second holes. Subsequent rotation of the retainer portion to the second position captures the lock-pin in the first and second holes, thereby joining the first structure to the second structure.